The STOBBE condensation with substituted succinic esters,part I. A Synthesis of Benzothiophene Derivatives

The condensation of some thienyl carbonyl compounds with dimethyl methylsuccinate in presence of potassium t-butoxide or sodium hydride gave predominantly the (E)-half-esters

1 i. e., CO₂CH₃ group and thiophene ring in trans-position. The nomenclature of cis/trans isomers used herein follows the IUPAC 1968 Tentative Rules, Section E, Fundamental Stereo-chemistry, J. Org. Chem. 35 , 2849 (1970). See also: J. E. Blackwood, C. J. Gladys, K. L. Loening, A. E. Petrarca, and J. E. Rush, J. Amer. chem. Soc. 90 , 510 (1968); Introduction to Subject Index of Chem. Abstr. 66 (1963).

1a – d , which were cyclised to benzothiophene derivatives 2a – d . The (E)-dibasic acids 6a – d were converted to the corresponding anhydrides 7a – d , which upon methanolysis produced the isomeric half-esters 8a – d . Treatment of 6d with concentrated sulphuric acid gave the cyclic ketonic lactone 9 together with the fluorenone derivative 10 .     

The STOBBE condensation with substituted succinic esters. Part IV. A Synthesis of Substituted Naphthalene and Maleic Anhydride

The condensation of piperonal with dimethyl phenylsuccinate using sodium hydride as condensing agent, gave predominantly the corresponding (E)-half-ester 1 . Cyclisation of this product led to the formation of the naphthalene derivative 2a , which upon hydrolysis produced the hydroxy acid 2b . The latter gave upon subsequent methylation and hydrolysis the naphthalene derivatives 2c, d . When benzaldehyde, p-chioro-, and p-methoxy-benzaldehydes were condensed under the above mentioned conditions, they produced the corresponding anhydrides 6a—c ; which were hydrolysed to the corresponding sodium salts 9 . The anhydride 6c gave with aniline the amide 7 .     

Organic Carbonates. Part XIII. Separation of Polar and Steric Effects in the Hydrolyses of Substituted Ethylene and Trimethylene Carbonates

The rate constants, the free energies (ΔF^#), the energies (ΔH^#) and entropies (ΔS^#) of activation, and the steric parameter of substituent (Es), for both the acid and the alkaline hydrolyses of four highly branched ethylene carbonates (Ia - d), and 11 trimethylene carbonates (IIa - k) were analysed according to Taft's procedure for a quantitative separation of polar and steric effects of alkyl substituents in the total effect of structure upon reactivity in hydrolysis. Application of Eq. (II) with Σσ* to the most hindered substrates (“α-axial methyl effect”) (IId - f) and to the moderately hindered substrates (IIa - c) gave well-separated parallel straight lines for the two groups. Deviations from Eq. (II) were manifested by the rate-enhanced group of compounds, geminally 2,2-disubstituted trimethylene carbonates (IIg - k) (“2,2-gem-dialkyl effect”), shown to exert a polar “field effect”; the assessment of its substituent constant σ_F* (= +0.17) is provided by Eq. (III). Analysis of 0¹⁸ exchange experiments and ΔΔF_A^# vs ΔΔF_B^# correlation (Eq. (IV)) show that the acid- and base-catalysed reactions occur in parallel via similar transition states, the attainment of each designating the rate-determining step in both systems. A value of 0.5 kcal/mole was found for the net steric interaction (E_S^B - E_S^A) exerted by an α-axial methyl substituent on the attacking hydroxide ion in attaining the transition state. It was concluded that in alkaline hydrolysis, the transition states of compounds exhibiting an “α-axial methyl effect” should closely resemble the tetrahedral intermediate (IX), while the transition states of the 2,2-gem-dialkyl series should more closely resemble the ground-state.     

Steric Effects in Di- and Tri-phenylmethane Dyes

The effect of crowding substituents on the electronic absorption spectra of di- and tri-phenylmethane dyes is reviewed.     

Steric and Electronic Effects in Basic Dyes

Lilolidine and 1-methylindoline analogues of some basic di- and tri-phenylmethane dyes have been prepared and their absorption spectra examined. Conjugation of the terminal nitrogen atoms with the aromatic rings is less efficient than in the corresponding julolidine and kairoline analogues. The presence of five-membered rings leads to a general instability of the dye-bases.     

Steric and Electronic Effects in Basic Dyes

Absorption spectra of several derivatives of Malachite Green containing more than one substituent in the phenyl ring have been examined. In most cases where steric effects are unimportant an additive relationship is found between the electronic effects of the substituents and the position of the first-frequency absorption band. The presence of a second unsaturated electron-withdrawing group in the phenyl ring leads to a further reduction in the intensity of the first band. In certain cases, the overall electron-withdrawal is such that the equilibrium between dye-base and univalent dye cation in acid solution is shifted in favour of the former species.     

Steric and Electronic Effects in Basic Dyes

Absorption spectra of nine derivatives of Malachite Green containing two or three methoxy groups in the phenyl ring have been examined. In the absence of varying steric effects an excellent additive relationship is found between the electronic effects of the substituents and the position of the first electronic absorption band. Conformational changes brought about by crowding substituents are detected by an increase in intensity of the first band accompanied by a decrease in intensity of the second band.     

Steric Effects in Stress Corrosion Fracture of Glass

Previous studies show that stress corrosion crack growth in glass is controlled by chemically enhanced crack tip bond rupture reactions. The brittle nature of fracture in glass suggests that the region where bond rupture reactions occur must be on the order of the atomic spacings in the material. Crack growth kinetics and zeolite diffusion data were used to determine the relation between molecular size and reactivity at the crack tip. Crack growth rates in silica glass were measured in the presence of a series of chemical species that have comparable chemical features and systematically increasing molecular diameters. Results show that chemically active species with diameters greater than 0.5 nm are ineffective as stress corrosion agents. A comparison of crack growth results and zeolite diffusion measurements was used to conclude that the opening to the crack tip is less than or equal to 0.5 nm. This crack tip dimension is consistent with the concept of atomic scale brittle fracture in silica glass.     

Kinetics of catalyzed acid/acid and acid/aldehyde condensation reactions to non-symmetric ketones

The kinetics and mechanism of acid and aldehyde condensations to produce non-symmetric ketones with CeO₂-based catalysts were studied using a combination of conventional and pulse microreactor tests. The effects of oxygen and water on the reactions were also studied.

Supported CeO₂ catalysts effectively catalyze the ketonization of acids at essentially complete conversion for extended periods, at weight hourly space velocities of 4–5. The optimal temperature range is 400–430 °C, depending on feed. Time on stream and number of regeneration cycles improved catalyst performance. Selectivities are improved by promotion with small amounts of potassium.

The acid/acid reaction to a typical methylketone proceeds roughly three times faster than the acid/aldehyde reaction, while the aldehyde/aldehyde initial reaction rate to desired methylketones is much slower; multiple aldol condensations predominate. When using acid/aldehyde feeds, water enhances ketone production, probably by supplying oxygen to the catalyst surface. While O₂ can fulfill a similar role, it also promotes combustion. Substitution of D₂O and CD₃COOH for water and acetic acid, respectively, led to kinetic isotope effects between 1.4 and 6.7, which is in the expected range for carboxylate decompositions.

Experiments at low conversion using CD₃COOH and either cyclopropanecarboxylic acid or its aldehyde showed that acetone and methylcyclopropylketone are formed preferentially as five D- and two D-atom isotopomers, respectively, for both acid/acid and acid/aldehyde feeds. This suggests the formation of a surface ketene intermediate, preferentially from acetic acid, which attacks a surface carboxylate to form the ketone, eliminating CO₂. The same conclusions could be drawn from ¹³C distributions in experiments using labeled acetic acid.     

The condensation/polymerisation of dimethyl siloxane fluids in a three-phase trickle flow monolith reactor

For the production of siloxane fluids, the viability of using a multi-channel monolith as a catalyst support system in a three-phase reactor has been studied. The catalyst was tripotassium phosphate (K₃PO₄). Experiments were performed in a single-channel flow reactor (15 mm i.d. and 500 mm catalyst coated length). The rate of reaction was followed by monitoring the disappearance of the hydroxyl group (–OH). Reaction experiments were performed at a hydroxyl group concentration range from 150 to 170 mol m⁻³, T=373–413 K and P=7.9 kPa with a nitrogen purge. The maximum temperature of operation was restricted to 413 K to avoid the formation of undesirable by-products. In the regime controlled by chemical kinetics, reaction was of an apparent first order with respect to –OH concentration, and in the apparent rate constant, the pre-exponential factor was 4.19×10⁻⁴ ms⁻¹, and the apparent activation energy was 16.1 kJ mol⁻¹. These are only valid for the operating pressure and purge gas flowrate used, as both of these are shown to affect water removal from the liquid phase and, hence, reaction rates. Mass transfer coefficients from the liquid to the catalyst surface were estimated and these increased rapidly with flowrate and were higher than expected for a falling liquid film.     

Preparation of zeolite‐incorporated poly(dimethyl siloxane) membranes for the pervaporation separation of isopropyl alcohol/water mixtures

ZSM‐5 zeolite‐incorporated poly(dimethyl siloxane) membranes were prepared, and the molecular dispersion of the zeolite in the membrane matrix was confirmed with scanning electron microscopy. After the swelling of the membranes was studied at 30°C, the membranes were subjected to the pervaporation separation of isopropyl alcohol/water mixtures at 30, 40, and 50°C. The effects of the zeolite loading and feed composition on the pervaporation performances of the membranes were analyzed. Both the permeation flux and selectivity increased simultaneously with increasing zeolite content in the membrane matrix. This was examined on the basis of the enhancement of hydrophobicity, selective adsorption, and the establishment of molecular sieving action. The membrane containing the highest zeolite loading (30 mass %) had the highest separation selectivity (80.84) and flux (6.78 × 10^?2 kg m^?2 h^?1) at 30°C with 5 mass % isopropyl alcohol in the feed. From the temperature dependence of the diffusion and permeation values, the Arrhenius activation parameters were estimated. A pure membrane exhibited higher activation energy values for permeability (E_p) and diffusivity (E_D) than zeolite‐incorporated membranes, and signified that permeation and diffusion required more energy for transport through the pure membrane because of its dense nature. Obviously, the zeolite‐incorporated membranes required less energy because of their molecular sieving action, which was attributed to the presence of straight and sinusoidal channels in the framework of the zeolite. For the zeolite‐incorporated membranes, the activation energy values obtained for isopropyl alcohol permeation were significantly lower than the water permeation values, and this suggested that the zeolite‐incorporated membranes had higher selectivity toward isopropyl alcohol. The E_p and E_D values ranged between 21.81 and 31.12 kJ/mol and between 15.27 and 41.49 kJ/mol, respectively. All the zeolite‐incorporated membranes exhibited positive values of the heat of sorption, and this suggested that the heat of sorption was dominated by Henry's mode of sorption. sorption. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1377–1387, 2005     

Rare earth (III) perfluorooctanesulfonates catalyzed synthesis of α-hydroxy-arylacetic acids from aryl methyl ketones in fluorous media

Ytterbium perfluorooctanesulfonate (Yb(OPf)₃) catalyzes the high efficient synthesis of α-hydroxy-arylacetic acids from aryl methyl ketones in the presence of SeO₂ in fluorous media. By simple separation, fluorous phase containing only catalyst can be used several times.     

First Modular Synthesis of Dissymmetric Biaryldiphosphine Ligands Allowing Tunable Steric and Electronic Effects

The first modular synthesis of a family of C₁‐symmetric diphosphine ligands is presented. Their synthesis is based on unprecedented highly regioselective halogen/metal interconversions on a common polybrominated biaryl precursor. This methodology allows the functionalization of the ortho‐ and ortho′‐positions of the biaryl core. Diphosphine ligands carrying only one substituent at the 6‐position and the two phosphine substituents at the 2‐ and 2′‐position become easily accessible. The two phosphine substituents may be identical (as in compounds 2 and 3 ) or different (as in compounds 1 and 4 ). All diphosphines were prepared on gram scale, and the enantiopure ligands were obtained by chromatography of the racemate on a chiral HPLC column. The asymmetric hydrogenation of β‐keto esters, acetamidocinnamates and dimethyl itaconate revealed good to excellent asymmetric inductions of up to 99 % ee, and are often close to those of the well‐known C₂‐symmetric MeO‐BIPHEP.     

Effects of surface free energy and nanostructures on dropwise condensation

Effects of surface free energy and nanostructures on dropwise condensation (DWC) were investigated experimentally. The oxidation and etching methods were applied to prepare the nanostructures on the copper substrates. Self-assembled monolayers coatings of n-octadecyl mercaptan were prepared on mirror-polished (SAM-2) and the nanostructured (SAM-1) copper substrates to promote the DWC. Experimental data presented that the nanostructure surface SAM-1 did not improve the dropwise condensation heat-transfer performance so much as to be expected for increasing the possible condensing surface area, compared to the mirror-polished SAM-2. This may be caused from the nanostructure's retardance to the condensate film. However, the incorporating effects of surface free energy and nanostructures of the condensing surface were found to play a really important role in the condensation heat-transfer enhancement. The fractal-like structures and the voids on SAM-1 surface were filled with condensate in the condensing process which resulted in a composite condensing surface of condensate and copper regions. Thus the average surface free energy of this composite condensing surface is larger than that of SAM-2 surface. The surface free energy difference between the condensate and the condensing surface of SAM-1 is less than that of SAM-2, so are the heat-transfer coefficients. The condensation heat-transfer is enhanced by a factor of 3 for SAM-2 surface, due to an increase of surface free energy difference between the condensate and condensing surface.     

合成异丙胺工艺技术研究进展

异丙胺是应用广泛的低级脂肪醇胺,主要用于医药和农药等领域。随着一些下游产品的开发,对异丙胺的需求量也随之增长。合成异丙胺主要有异丙醇催化加氢胺化法和丙酮加氢催化胺化法。采用何种方法优势更大,主要取决于原料价格。镍基催化剂价格低廉,活性较高,是今后催化剂研究重点。丙酮法工艺成熟,但反应中副产物较多,生产成本较高;异丙醇反应副产物较少且易控制。     

Synthesis and thermotropic liquid‐crystalline behavior of novel main‐chain poly(aryl ether ketones)

Novel aromatic poly(ether ketones) containing bulky lateral groups were synthesized via nucleophilic substitution reactions of 4,4′‐biphenol and (4‐chloro‐3‐trifluoromethyl)phenylhydroquinone (CF‐PH) with 1,4‐bis(p‐fluorobenzoyl)benzene. The copolymers were characterized by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction, and polarized light microscopy observation. Thermotropic liquid‐crystalline behavior was observed in the copolymers containing 40, 50, 60, and 70 mol % CF‐PH. The crystalline–liquid‐crystalline transition [melting temperature (T_m)] and the liquid‐crystalline–isotropic phase transition appeared in the DSC thermograms, whereas the biphenol‐based homopolymer had only a melting transition. The novel poly(aryl ether ketones) had glass‐transition temperatures that ranged from 143 to 151°C and lower T_m's that ranged from 279 to 291°C, due to the copolymerization. The polymers showed high thermal stability, and some exhibited a large range in mesophase stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1347–1350, 2003     

Charge transfer copolymerization and properties of isopropyl methacrylate with acrylonitrile and methacrylonitrile

Isopropyl methacrylate (IPMA) with Acrylonitrile (AN) and Methacrylonitrile (MAN) copolymers of different copositions were prepared at 60°C and 80°C, respectively, using a mixture of n-Butylamine (nBA) and carbon tetrachloride (CCl₄) in dimethyl sulphoxide (DMSO) as a charge transfer (CT) initiator. The percentage composition of the copolymers was established by elemental analysis. The copolymerization reactivity ratios were computed by the Kelen–Tudos method. In both the systems, IPMA was found to be more reactive; the copolymers sequence was random in nature. The copolymers were characterized by IR, ¹H-NMR, ¹³C-NMR spectroscopy and intrinsic viscosity measurements in dimethyl formamide (DMF) at 30±0.1°C. The thermal behavior of the AN-IPMA copolymers was studied by thermogravimetry (TG) in air. The thermal stability increased, with increasing AN content in the copolymer chain. The solubility parameter of AN-IPMA copolymer was evaluated by studying the intrinsic viscosity in different solvents. The solubility parameter of the copolymer was found to be 9.7 (cal/cc)^1/2.     

Fractionation with condensation and evaporation in wetted-wall columns

A model is presented to describe the behavior of falling film fractionators with evaporation or condensation. Experimental measurements of vapor composition, vapor temperature and wall temperature profiles were made. Close agreement suggests that the model is applicable to both adiabatic and nonadiabatic conditions.